Condensate Mass Research Articles

Investigation of the condensation mass transfer time relaxation parameter for numerical simulation of the thermosyphon

The condensation mass transfer time relaxation (rc) is a critical empirical factor that reflects the change in the process from a non-equilibrium state and indicates the rate of the condensation. The determination of rc in the Lee model is crucial for the Computational Fluids Dynamics (CFD) simulation of thermosyphons. In this paper, the relationship between rc and internal parameters influencing the heat transfer performance of the thermosyphon are investigated in detail. The effects of working fluid properties, saturation temperature, filling ratio, and heat input on the temperature distribution of the wall surface of the thermosyphon were studied. Moreover, the corresponding CFD model of the thermosyphon was established. The result indicated that the simulated average condenser temperature rises with increasing rc and gets closer to the experimental average temperature in the form of a log function. By comparing the experimental data with the simulation results, the appropriate rc values for various conditions were determined to be around 104 s−1, within a margin of error of 1.5%. The empirical relationship equations of rc were fitted with experimental results to the key parameters. It was found that the effect on rc of vapor density was relatively minor, while the effect of the filling ratio was the most significant. By applying the obtained relational expression, the simulation results are in good agreement with other references, proving the accuracy and applicability of the calculations. This paper aims to refine the thermosyphon model and, facilitate the exploration of the phase-change heat and mass transfer mechanism of two-phase flow.

Experimental study of condensation characteristics and operation strategies of induction radiant air-conditioning system

To study the operation and condensation characteristics of an induction radiant air-conditioning system as a novel system that combines induction ventilation and radiant air conditioning, the characteristics of convection and condensation of an indoor terminal device radiant induction unit were studied. The mass transfer coefficient, condensation temperature, and condensation rate were analyzed experimentally. The time required to achieve a steady state indoor thermal environment was collected. The results indicated that the primary airflow rate and temperature mainly affected the mass transfer coefficient, condensation temperature, and condensation rate. When the indoor thermal environment reached a steady state, the heat transfer performance of the radiant induction unit was mainly affected by the primary air temperature. When condensation occurred, the primary airflow rate had a greater influence on the condensation rate. The start-up and response performances of the system were better than those of a traditional radiant air-conditioning system. In the condensation condition, reasonable control strategies maintain the primary air temperature and adjust the primary air flow rate, which can ensure sufficient heat transfer and stabilize the indoor thermal environment faster.

Estimating Phase Transition Rates in Shallow Cumulus Clouds from Mass Flux. Part I: Theory and Numerical Simulations

Abstract The system of trade wind cumulus clouds observed during the RICO field project was simulated by an LES model in a domain of the size of a mesoscale model grid. More than 2000 clouds were analyzed by stratifying them by their cloud-top heights. The investigation was focused on phase transition rates (TR), which in warm tropical clouds are represented by the processes of condensation/evaporation. We previously demonstrated, based on LES data, that a nearly perfect correlation (R = 0.99) exists between upward mass flux (MFP) and condensation rate (CR), and that the correlation between MFP and evaporation rate (ER) is only slightly lower (R = 0.98). The strong dependence of TR on MFP and the linear relationship between them were explained by applying condensation theory and the concept of “quasi-steady” supersaturation. The LES-derived slope of the linear TR–MFP relationship agreed with its theoretical value, with an error of less than 5%. This result implies that supersaturation in clouds, on average, varies within a few percentage points of its quasi-steady value. In our analysis we considered parameters characterizing cloud as a whole, that is, parameters integrated over the cloud volume. However, condensation theory and LES data show that the linear fit is applicable to local variables and therefore may be integrated to obtain relationships for horizontally averaged variables. Expanding the TR–MFP relationship to vertically dependent variables may provide the framework for development of subgrid-scale latent heat release parameterization. Significance Statement This study investigated condensation/evaporation processes in tropical cumulus clouds. The energy exchanged during these processes is an important driving force behind a wide range of atmospheric phenomena. We found theoretically, and confirmed in computer simulations, that the rate of condensation/evaporation can be expressed as a linear function of the cloud vertical velocity. This finding suggests a new approach to calculate cloud energy transformations in numerical weather prediction models.

Catalytic cracking of castor oil via microwave assisted method

Castor oil extracted from seeds of Ricinus Communis plant has an immense potential being used to yield valuable hydrocarbons with shorter chain length. Castor oil contains chemical structures of heavy hydrocarbons and long chains may undergo a cracking process which are similar to that as in petrochemical industries. However, cracking process requires extremely high temperature and energy input. This research came by with an attempt to reduce waste of energy using both microwave assisted method and modified metal catalyst, Zn/ZSM-5 to provide sufficient energy for cracking process to occur at comparatively low temperature. Wet impregnation method was used for Zn/ZSM-5 catalyst preparation and the experiments were carried out via microwave-assisted method. The microwave effect on the temperature and mass of condensate formed was investigated at three different output powers; 650, 700 and 750 W, under different Zn/ZSM-5 concentrations; 5, 8 and 10 wt% for 1 h. Results showed that cracking of castor oil is feasible at low temperature (<250 °C) using modified Zn/ZSM-5 via microwave assisted method. The highest yield of total mass of condensate (5.61%) was obtained from 750 W output power and 10 wt% Zn/ZSM-5 catalyst concentration. In addition, the highest cracking percentage (97.7%) was obtained from 750 W output power and 5 wt% Zn/ZSM-5 catalyst concentration. Valuable cracked compounds such as octane for fuel products and undecylenic acid for pharmaceutical uses were obtained.

A contribution for the study of RTM effect in height anomalies at two future IHRS stations in Brazil using different approaches, harmonic correction, and global density model

AbstractThe high-frequency effects of the gravity field can be obtained from residual terrain modeling (RTM) technique. However, for the International height reference system (IHRS), this is an open problem. Over the last decades, various approaches have been proposed for the practical solution of Newton’s Integral, such as point-mass, tesseroid, prism, and polyhedron. Harmonic correction (HC) and the use of more realistic mass density values have also been studied. In this work, in order to calculate RTM height anomalies at BRAZ and PPTE IHRS future stations in Brazil, such approaches and issues have been evaluated. Density values have been obtained from CRUST 1.0 global model. For the HC, the traditional mass condensation technique and Poisson’s equation have been used. The resulting values proposed by different approaches are very close to each other, with differences at the submillimeter-level. The RTM height anomaly values reached 1.5 and 1.4 mm at the BRAZ and PPTE stations, respectively. HC at BRAZ station can be disregarded without prejudice since its order of magnitude was 10−5 m. The use of CRUST 1.0 density values has proposed slight improvements of 0.8 and 0. 4 mm at BRAZ and PPTE station, respectively, in relation to the use of Harkness constant density value.

Synthetic Lyman-α emissions for the coronagraph aboard the ASO-S mission

Context. Strong ultraviolet (UV) emission from the sun will be observed by the Lyman-α Solar Telescope (LST) on board the Advanced Space-based Solar Observatory (ASO-S), scheduled for launch in 2022. It will provide continuous observations from the solar disk to the corona below a 2.5 solar radius with high resolution. To configure the appropriate observing modes and also to better understand its upcoming observations, a series of simulations and syntheses of different structures and processes need to be done in advance. Aims. As prominence eruptions are the main drivers of space weather, the need to monitor such phenomena has been set as a priority among the objectives of ASO-S mission. In this work, we synthesize the evolution of a modeled prominence-cavity system before and during its eruption in the field of view (FOV) of LST. Methods. We adopted the input magnetohydrodynamic (MHD) model of a prominence-cavity system, which is readily comparable to the Atmospheric Imaging Assembly (AIA) observations. The Lyman-α emission of the prominence and its eruptive counterparts are synthesized through the PRODOP code, which considers non-local thermodynamic equilibrium (NLTE) radiative transfer processes, while the other coronal part such as the cavity and surrounding streamer, are synthesized with the FORWARD package, which deals with optically thin structures. Results. We present a discussion of the evolution of the eruptive prominence-cavity system, analyzing the synthetic emissions both on the disk near the limb and above the limb as viewed by the coronagraph, as well as the three-dimensional (3D) data of the MHD simulation. Conclusions. The evolution of the prominence-cavity system exhibits the condensation of cavity mass onto the prominence and the evaporation of prominence plasma into the central cavity. The synthetic emission in Lyman-α shows a similar pattern as in the AIA extreme ultraviolet (EUV) wavelengths before eruption, namely, the appearance of a “horn” substructure as a precursor to the eruption. The emission of prominence with an optically thick assumption is one to two orders of magnitude lower than the optically thin one. Here, the dimming effect in Lyman-α is analyzed, for the first time, for the eruptive prominence-cavity system. Accompanying the prominence plasma motion during the eruption, the apparent dimming shows a preferred location evolving from the top and bottom of the bright core to the whole body above the bottom part, while the collisional component progressively dominates the total emission of the flux rope bright core at these locations. By analyzing the signal-to-noise ratio (S/N) with a consideration of LST’s optical design, we conclude that the substructures in the cavity and the bright core of the CME can be observed with sufficient S/N at different stages in the FOV of LST.

A combined cooling and power transcritical CO2 cycle for waste heat recovery from gas turbines

• A combined cooling and power cycle working with CO 2 is proposed for waste heat recovery from a gas turbine. • Efficiencies of the combined system and its COP are evaluated for three configurations (simple, split and cascade) versus different cycle parameters. • Although the split configuration has the highest net power generation at high and moderate heat source temperatures, in the case of low temperature waste heat from the gas turbine (less than 420 °C), net power of the simple cycle surpasses and the split cycle gives the lowest net power. • The split configuration yields the highest thermal efficiency between the three investigated configurations except at low condenser pressures. • The split cycle has a slight supremacy in heat recovery efficiency at intermediate and high gas turbine exhaust temperatures. This supremacy persists over all the investigated cycle parameters. • For low CO 2 mass fractions into the refrigeration part, cascade configuration has the highest COP. • For high CO 2 mass fractions into the refrigeration part, simple configuration has the highest COP. • The split cycle is the most efficient configuration regarding the total system efficiency. Hence, it can be selected as the candidate cycle configuration for further optimization in a future study. A transcritical carbon dioxide (T-CO 2 ) cycle is analyzed for waste heat recovery from a gas turbine. The cycle is proposed to produce combined power and cooling using carbon dioxide as a single pure working fluid. Simple, cascade and split cycle configurations are compared for power generation using a recuperator while a low-temperature loop is added for the cascade and split cycles. In a previous report in the literature the power generation part alone was presented for the three configurations and it was concluded that the split cycle can produce the highest power among the three systems. Here, the same configurations are studied combined with a compression refrigeration cooling effect with the same working fluid, and a parametric study is conducted. The power cycle is a T-CO 2 cycle which absorbs the waste heat from a gas turbine. The effect of different parameters like cooling load, splitters mass fractions, turbine pressure and condenser pressure are investigated and a comparison between the three configurations are demonstrated. It is shown that, for instance, in case of higher temperatures of gas turbine exhaust the split configuration has the highest net power production while using gas turbine exhaust flow of temperatures less than 420 °C the simple configuration produces the maximum output power. From the cooling perspective, for values of turbine inlet pressure higher than 222 bar, abs. the cascade cycle indicates the best cooling performance while the split one takes this position at lower turbine inlet pressures.

Condensation–mass flux connection in warm convective clouds: theory and implications for cloud supersaturation

Abstract. The study focused on the relationship between Condensation Rate (CR) and the upward/Plus Mass Flux (MFP) in a system of trade wind cumulus clouds simulated by an LES model. The model was initialized with data observed during the RICO field project, and simulated in a 50.0×50.0 km horizontal domain. In our previous study (Kogan, 2021) we showed that a nearly perfect correlation exists between CR and MFP (correlation coefficient R=0.99). As a result, condensation rate can be highly accurately expressed as a linear function of upward mass flux. This LES derived finding was explained using condensation theory and concept of quasi-steady supersaturation. The obtained from the LES model slope of the CR–MFP linear fit was in excellent agreement with its theoretical value (error less than 5 %). The theory also showed that the equality between the LES and theoretical values of the slope follows from the equality between supersaturation and its quasi-steady value. The study results suggest that condensation rates, for a variety of cloud conditions, can be precisely estimated using the single variable–upward mass flux. Possible implications of the results for evaluating supersaturation and degree of non-adiabaticity in clouds are discussed.

Vacuum Low-Temperature Microwave-Assisted Pyrolysis of Technical Lignins

Cleavage by microwave-assisted pyrolysis is a way to obtain higher-value organic chemicals from technical lignins. In this report, pine kraft lignin (PKL), spruce and beech organosolv lignin (SOSL and BOSL), and calcium lignosulfonates from spruce wood (LS) were pyrolyzed at temperatures between 30 and 280 °C using vacuum low-temperature, microwave-assisted pyrolysis. The mass balance, energy consumption, condensation rate, and pressure changes of the products during the pyrolysis process were recorded. Phenolic condensates obtained at different temperatures during pyrolysis were collected, and their chemical composition was determined by GC-MS and GC-FID. The origin of the technical lignin had a significant influence on the pyrolysis products. Phenolic condensates were obtained in yields of approximately 15% (PKL and SOSL) as well as in lower yields of 4.5% (BOSL) or even 1.7% (LS). The main production of the phenolic condensates for the PKL and SOSL occurred at temperatures of approximately 140 and 180 °C, respectively. The main components of the phenolic fraction of the three softwood lignins were guaiacol, 4-methylguaiacol, 4-ethylguaiacol, and other guaiacol derivatives; however, the quantity varied significantly depending on the lignin source. Due to the low cleavage temperature vacuum, low-temperature, microwave-assisted pyrolysis could be an interesting approach to lignin conversion.

Stabilization of spatiotemporal dissipative solitons in multimode fiber lasers by external phase modulation

In this work, we introduce a method for the stabilization of spatiotemporal (ST) solitons. These solitons correspond to light bullets in multimode optical fiber lasers, energy-scalable waveguide oscillators and amplifiers, localized coherent patterns in Bose–Einstein condensates, etc. We show that a three-dimensional confinement potential, formed by a spatial transverse (radial) parabolic graded refractive index and dissipation profile, in combination with quadratic temporal phase modulation, may permit the generation of stable ST dissipative solitons. This corresponds to combining phase mode-locking with the distributed Kerr-lens mode-locking. Our study of the soliton characteristics and stability is based on analytical and numerical solutions of the generalized dissipative Gross–Pitaevskii equation. This approach could lead to higher energy (or condensate mass) harvesting in coherent spatio-temporal beam structures formed in multimode fiber lasers, waveguide oscillators, and weakly-dissipative Bose–Einstein condensates.

Dimensionless Profiles of Temperature and Steam Mass Fraction in Flows of Steam-Air Mixtures on a Flat Plate

Abstract Wall functions are generally used in a turbulent analysis with a computational fluid dynamics (CFD) code and large computation cells. The logarithmic law based on the analogy between momentum, energy, and mass transfer is widely used in wall functions for turbulent flows, but its validity in the turbulent boundary layer has not been confirmed for dimensionless profiles of temperature and steam mass fraction in flows of steam and noncondensable gases. In this article, therefore, we evaluated dimensionless profiles of temperature and steam mass fraction in flows of steam and air on a flat plate by using existing data. From the heat and mass transfer equations at the condensation surface based on the gradient of temperature or steam mass fraction, we showed that the convection heat flux qconv (which is used for the definition of the dimensionless temperature T+) should include the term of condensate mass flux ms and that the dimensionless steam mass fraction Ys+ should be a function of the dimensionless distance y+ (= uτ y/ν where uτ is the friction velocity), the Schmidt number Sc and the air mass fraction (1−Xs). Values obtained from the newly defined T+ and Ys+ and the existing data agreed relatively well with the linear function near the viscous sublayer (a few data points were there) but were much smaller than the existing logarithmic law due to condensation in the turbulent boundary layer (i.e., mist generation). On the other hand, the T+ and Ys+ values obtained by using the local Nusselt number Nuy and the local Sherwood number Shy (which were proposed in our previous study), respectively, agreed well with the logarithmic law.

Theory of In-Cloud Activation of Aerosols and Microphysical Quasi-Equilibrium in a Deep Updraft

Abstract The microphysical quasi-equilibrium in an ascending adiabatic parcel is elucidated by an analytical theory in 0D with drastic simplifications. The theory predicts how in-cloud activation is most likely to be triggered by the onset of precipitation during sufficient ascent, with the ascent only needing to approach almost twice the cloud-base updraft speed aloft. The precipitation and cloud condensate mass fields are coupled in a closed system in a simplified version of the model. The initial state of no precipitation is unstable with respect to a perturbation. In the 2D phase space of both mass fields, there is a neutral line. Unstable growth of precipitation mass drives the system to cross the line into a regime of stability. An attractor is then approached consisting of precipitation mass balanced by accretion of cloud mass and fallout. The cloud-particle number concentration also approaches a stable equilibrium governed by the balance between in-cloud activation aloft from the inexorably increasing supersaturation during vertical acceleration and accretion of cloud droplets by precipitation. Dimensionless numbers characterizing the microphysical equilibria and their stability are derived mathematically, including a condensation–precipitation efficiency and an in-cloud activation efficiency. The theory explains common observations of the orders of magnitude of liquid water content in convective and stratiform clouds. Finally, sensitivity tests of the numerically integrated theoretical equations are documented with respect to variations in cloud condensation nucleus (CCN) aerosols and updraft speed. It is shown that this theory of in-cloud activation, with an increasing supersaturation during ascent, applies to both ice-only and liquid-only cloud. Significance Statement The purpose of the study is to create a theory for how equilibria among cloud-microphysical properties are attained during ascent. Continual initiation of fresh cloud droplets far above cloud base in the free troposphere is explained. The theory proposes a balance between creation and depletion of such droplets, in relation to a balance between creation and fallout of precipitation. The transition from positive feedbacks of instability toward negative feedbacks of stability when the equilibria are approached is elucidated. The theory explains why the mass content of cloud liquid in regions of ascent is typically about an order of magnitude lower in layer clouds with weak ascent than in convective clouds with faster ascent. Any future work could extend the theory to treat dilute parcels or coexistence of supercooled liquid and ice.

Color-flavor dependence of the Nambu-Jona-Lasinio model and QCD phase diagram

We study the dynamical chiral symmetry breaking/restoration for various numbers of light quarks flavors and colors using the Nambu-Jona-Lasinio (NJL) model of quarks in the Schwinger-Dyson equation framework, dressed with a color-flavor dependence of effective coupling. For fixed and varying , we observe that the dynamical chiral symmetry is broken when exceeds its critical value . For a fixed and varying , we observe that the dynamical chiral symmetry is restored when reaches its critical value . Strong interplay is observed between and , i.e., larger values of tend to strengthen the dynamical generated quark mass and quark-antiquark condensate, while higher values of suppress both parameters. We further sketch the quantum chromodynamics (QCD) phase diagram at a finite temperature T and quark chemical potential μ for various and . At finite T and μ, we observe that the critical number of colors is enhanced, whereas the critical number of flavors is suppressed as T and μ increase. Consequently, the critical temperature , , and co-ordinates of the critical endpoint in the QCD phase diagram are enhanced as increases and suppressed when increases. Our findings agree with the lattice QCD and Schwinger-Dyson equations predictions.

An Exact and Comparative Analysis of MHD Free Convection Flow of Water-Based Nanoparticles via CF Derivative

Convective flow is a self-sustained flow with the effect of the temperature gradient. The density is nonuniform due to the variation in temperature. The effect of the magnetic flux plays a major role in convective flow. The process of heat transfer is accompanied by a mass transfer process, for instance, condensation, evaporation, and chemical process. Combination of water as base fluid and three types of nanoparticles named as copper, titanium dioxide, and aluminum oxide is taken into account. Due to the applications of the heat and mass transfer combined effects in different fields, the main aim of this paper is to do a comprehensive analysis of heat and mass transfer of MHD natural convection flow of water-based nano-particles in the presence of ramped conditions with Caputo–Fabrizio fractional time derivative. The exact fractional solutions of temperature, concentration, and velocity have been investigated by means of integral transform. The classical calculus is assumed as the instant rate of change of the output when the input level changes. Therefore, it is not able to include the previous state of the system called the memory effect. But, in the fractional calculus (FC), the rate of change is affected by all points of the considered interval to incorporate the previous history/memory effects of any system. Due to this reason, we applied the modern definition of fractional derivative. Here, the order of the fractional derivatives will be treated as an index of memory. The influence of physical parameters and flow is analyzed graphically via computational software (MATHCAD-15). Our results suggest that the incremental value of the M is observed for a decrease in the velocity field, which reflects to control resistive force.

Numerical Simulations of Laminar Film Condensation of H2O/Air or H2O/CO2 on a Vertical Plate

The liquid film thickness seriously affects the distribution of temperature, velocity, and components near the interface for steam condensation in the presence of small concentration noncondensable gas. The liquid film thickness for H2O/CO2 forced convection condensation separation on vertical plate has not been studied numerically. Thus, volume of fluid model and a phase change model were used to study steam condensation in the presence of noncondensable gases. The calculations studied the effects of velocity, surface subcooling, and noncondensable gas mole fraction on the heat transfer for H2O/air or H2O/CO2 mixtures. The results show that the predicted heat transfer coefficients agree well with previous experimental data. The gas and liquid film thicknesses controlling the condensation heat transfer in the presence of a noncondensable gas become thicker as the mixture flows along the cooled wall. The condensate mass flow rate and the heat transfer coefficient are both seriously reduced by the noncondensable gas. The condensate heat transfer in the presence of noncondensable gases is mainly determined by the diffusion coefficient and the thermal conductivities of the components in the gas film layer.

Revealing Bias of Cloud Radiative Effect in WRF Simulation: Bias Quantification and Source Attribution

AbstractAccurate prediction of cloud radiative effect (CRE) is important to weather forecast and climate projection, and solar energy production—a major renewable energy source toward decarbonization. Here, we evaluate the capability of the Weather Research and Forecast (WRF) model to simulate solar irradiance on a short‐term timescale (days) against observations in a remote region in north China. Results illustrate that our WRF simulation systematically underestimates the CRE and three error sources are identified: (a) incorrectly predicted cloud occurrence (i.e., missed clouds and false clouds), (b) underestimated cloud condensate mass, and (c) simplified parameterization of solar irradiance extinction. The incorrect cloud occurrence is the leading bias source, because it occurred most frequently and results in a substantial magnitude of errors. The cloud occurrence bias is subject to simulations of large‐scale air ascends and planetary boundary layer turbulence. Even when cloud occurrence is correctly simulated, our WRF simulation still underestimates CRE. This is because (a) the shallow convection scheme and cloud microphysics scheme underestimate cloud condensate mass and (b) cloud water path that feeds in the radiation scheme neglects precipitating cloud condensates (i.e., raindrops and graupels). Furthermore, an evaluation of cases with small bias in cloud condensate mass and effective radius demonstrates the parameterization of solar irradiance extinction for clouds induces a mean root mean square deviation of 110 W/m2. A possible reason is the simplified calculation of cloud extinction efficiency by applying Monte Carlo integration. The gained knowledge is important for understanding CRE simulation and solar irradiance forecast.

Numerical investigation on direct contact condensation-induced water hammer in passive natural circulation system for offshore applications

For the passive natural circulation systems (PNCSs) in offshore floating nuclear plants, the ocean environment is usually regarded as the final heat sink. Condensation-induced water hammer (CIWH) may occur as the saturated steam released into the ocean by natural circulation. This study aims to develop a CFD model to analysis the CIWH phenomenon induced by direct contact condensation (DCC) in the PNCSs. In the model framework, the two-phase interface is tracked explicitly by the volume of fluid method; the interface heat transfer is acquired by the hybrid Heat Transfer Coefficient model based on the Surface Renewal Theory; the condensation heat and mass transfer rate are obtained by user-defined functions (UDF). The condensation model is firstly validated with the PMK-2 experimental data, showing consistency with the measured temperature evolutions. Then, the model is applied to investigate the CIWH events in the horizontal pipe geometry of the passive natural circulation systems. The simulation results indicate that the reverse flow of subcooled water triggers the formation of the CIWH events, by increasing the condensation rate and forming the entrapped bubble. The reverse flow periodically occurs afterwards, inducing multiple CIWHs. The increase of inlet stream velocity lengthens the reverse flow period and the distance, thus strengthening the interfacial condensation and the pressure impulse of CIWH.

Experimental investigation on condensation inside of storage tanks during rapid cooling in a heavy rain event

Experiments have been performed on a 2.6 m3 gas and liquid filled vertical storage tank at ambient conditions that has been cooled with cold water. The breathing volume flow and main parameters, such as gas and wall temperatures, condensate masses generated and tank differential pressure have been measured. The experiments have been performed with dry air, water and methanol as storage media. The aim is to obtain validation data for future models and correlations for cooling of storage tanks. Additionally, the impact of fog formation in the tank atmosphere, dropwise and film condensation and rain intensity during heavy rain events on the maximum breathing flow rate have been investigated. As a result of the analysis of physical phenomena during the cooling of the tank, an increase in the maximum breathing volume flow for storage media with increasing vapor pressure was observed. Strong fog formation was visible in all experiments with condensable liquids. In contrast to alcoholic storage media, dropwise condensation on the wall is expected when storing aqueous media. Rain intensity and heat transfer models from literature were examined regarding the sizing of tank breathing valves. Deviations between experimental data and a typical manual calculation model for sizing of tank breathing devices varied between 13% and 143%. The validation on the experimental data clearly showed that current models are not suitable for describing the breathing volume flow rate that occurs during sudden heavy rain events with sufficient accuracy.

Simultaneous measurement of heat flux and droplet population during dropwise condensation from humid air flowing on a vertical surface

A new experimental apparatus for the investigation of dropwise condensation from humid air flowing over a vertical aluminum surface at controlled velocity is presented. Differently from other works on this subject, here we measure simultaneously, during condensation of flowing moist air, the total heat flux (by a heat flux sensor), the latent heat flux (by weighing the mass of condensate), the small and the large droplet population. Experimental tests were performed on two aluminum specimens that display different wettability: a mirror-polished surface (56° advancing contact angle, 46° contact angle hysteresis) considered as a baseline, and a coated surface functionalized by using a sol–gel coating (87° advancing contact angle, 15° contact angle hysteresis). The effects of the wall subcooling, moisture content, relative humidity and air velocity on the heat and mass transfer during dropwise condensation (DWC) are investigated. Enhanced condensation is observed on the coated surface but, with the increase of relative humidity and wall subcooling, the advantage of using the coated surface diminishes. Time-lapse videos of the condensation process, featuring droplets detection down to three microns, are used to investigate droplet population (both large and small droplets) and nucleation sites density. Usually, DWC models assume tentative values of the nucleation site density and tentative trends of the droplet population. In this paper we measure and discuss such parameters. The determination of the nucleation site density is crucial because it affects the droplet interactions and the drop size distribution, determining the overall heat transfer. The measurement of the nucleation site density is currently rare in the literature, especially during condensation of flowing humid air. Here the nucleation site density is determined with a double approach and it is found to vary between 3.3 × 108 sites/m2 and 6.1 × 108 sites/m2 in the investigated range of experimental conditions. The experimental droplet population is also compared against the predicted one, finding some disagreement which should be properly addressed for the development of improved DWC models.

Electric fuel conversion with hydrogen production by multiphase plasma at ambient pressure

Reactive species in the plasma interact with both liquid hydrocarbons and natural gas at the gas–liquid interface producing desired intermediate molecules and hydrogen. Electric (plasma) conversion of fuels. Traditional fuel processing uses combustion and heat for conversion. Through plasma processing we show electricity can be used to convert fuels more efficiently and as economically as traditional processing. A fossil fuel processing industry based on electricity is more flexible, cleaner, greener, and can transition to a future based on renewable energy and liquid fuels. • Transient multiphase non-thermal plasma efficiently integrates renewable energy into chemical change. • High conversion (50%) to high quality products and low energy cost (<$4/barrel). • Operating at near ambient conditions, robust and easy to manufacture and maintain. • Adaptable to renewable energy sources minimizing GHG emissions. Electrifying refinery for unconventional/heavy oils, significant emission reductions, and alternative/bio fuels, faces major technological challenges: conversion, energy efficiency, modularity and integration with renewable electricity. Here, we introduce a multi-phase non-thermal plasma reactor that uses electrical discharges to co-convert liquid fuel and natural gas. Normal hexadecane was treated with methane plasma to validate conversion chemistry, and quantify the pathways of vapor, condensate, liquid and residue mass conversion. A complete mass balance and characterization of all products were determined. Using 500 kJ/kg-hexadecane energy input (∼1% of hexadecane’s energy content) this plasma process co-converts 9.36% of the hexadecane and 20% of the methane by mass. Distribution of products are: 2.18% hydrogen, 45.9% C 2 -C 4 , 28.9% high octane gasoline (C 5 -C 11 ), 16.4% diesel (C 12 -C 18 ), 2.78% heavier hydrocarbons, and 1.7% coke. Lighter product yields (C 5 -C 15 ) were ∼ 9 molecules/100 eV, and modeled by a molecule dissociation mechanism. Hydrogen yield was 34.8 kWh/kg-H 2 with minimal GHG emissions. Plasma-chemical conversion efficiency was ∼ 30%. This conversion process has higher efficiency, and reduces GHG emission compared to traditional technologies.